Apparatus for causing signals at random intervals



March 14, 1967 B. s. BAKER 3,309,541

APPARATUS FOR CAUSING SIGNALS AT RANDOM INTERVALS 2 Sheets-Sheet 1 Filed May 21, 1965 mw T0 m5 V/ N l w d C ll 0 F/GZ United States Patent Ofiice 3,309,541 Patented Mar. 14, 1967 3,309,541 APPARATUS FOR CAUSING SIGNALS AT RANDOM INTERVALS Bernard Stuart Baker, Coventry, England, assignor t Courtaulds Limited, London, England, a company of Great Britain Filed May 21, 1965, Ser. No. 457,759 2 Claims. (Cl. 307-106) This application is a continuation-in-part" application of my prior co-pending application Ser. No. 185,019 now abandoned filed Apr. 4, 1962, which itself is a continuation-in-part application on my abandoned application Ser. No. 852,688 filed Nov. 13, 1959.

Certain industrial and other processes require that certain steps should occur at irregularly spaced intervals of time. For example, in the production of textile effects threads such as slub-yarns, it is important that the slub or similar effect should not be repeated in such a fashion that undesirable patterning appears in textile material woven or knitted from such yarns.

The present invention relates to a circuit for producing an impulse train with an approximately statistically defined distribution and enables the range of time intervals between occurrences to be selected so that minimum and maximum time intervals can be defined.

According to the invention apparatus for generating signals at irregular time intervals comprises in combina-- tion, an electrical wave-form generator, first and second condensers, first and second relays, a change-over switch connected by said first relay to connect said second condenser alternately to said generator and to said second relay, and a change-over switch actuated by said second relay to connect said first condenser alternately to said generator and to said first relay, and output means operated by at least one of said relays for altering the condition of an adjacent system.

Preferably each condenser discharges at a substantially uniform rate.

The frequency of the waveform generator may be varied in a random manner, preferably by having a series of fixed frequencies available and selecting these frequencies in turn in synchronism with the switching.

The waveform is preferably triangular, but other waveforms, for example a sinusoidal waveform, may be used.

An example of a simple circuit in accordance with the invention is illustrated diagrammatically in the accompanying drawings, in which:

FIGURE 1 is a schematic representation of the circuit;

FIGURE 2 is a series of graphs illustrating the principles behind the method of operation of the circuit shown in FIGURE 1;

FIGURE 3 schematically illustrates a more comprehensive circuit for the control of a slub producing apparatus which is based upon the system illustrated in FIGURE 1 which comprises three generators and which produces a signal determining the slub spacing, length and thickness;

FIGURE 4 illustrates the signal train produced by the circuit of FIGURE 3; I

FIGURE 5 illustrates an alternative circuit arrangement, enabling a slub producing apparatus to be controlled from two generators only, and

FIGURE 6 is a graph illustrating the probability of a given time interval occurring within themaximum and minimum limits established by the invention.

FIGURE 1 shows a circuit comprising a waveform generator 1 which can be connected by two-way switches 2 and 5 to either of two similar loops, each comprising a condenser and a relay-containing discharge circuit, commonly connected to ground and so back to the generator 1. The switches 2 and 5 can selectively connect the condensers of their respective loops either to the generator 1 for charging them or into the loops for discharging them through the respective discharge circuits. Each of the two-way switches 2 and 5 is controlled by the relay of the discharge circuit in the other loop. Thus the upper loop in FIGURE 1 comprises a condenser 3 and relay-containing discharge circuit 4 the relay of which controls two-way switch 5 of the lower loop. The lower loop comprises a condenser 6 and a relay-containing discharge circuit 7 the relay of which controls the twoaway switch 2. The switches 2 and 5 are contacts of the relays of circuits 7 and 4 respectively and are normally urged by springs to their right hand positions, but when the relays are energised they move the respective switches to their left hand positions. The relays of circuits 4 and 7 are of the usual electromagnetic type comprising a solenoid through which an electric current can be passed, a current of sufiicient magnitude causing an armature to be moved to move the relay contacts against the action of their springs, that is to move the switches 2 and 5 to their left hand positions in the drawing. When the switches 2 and 5 are respectively in their left hand positions the condensers 3 and 6 will be charged by the generator 1, and when the switches are reversed to their right hand positions the condensers will be isolated from the generator and can discharge through the circuits 4 and 7. V

The circuits 4 and 7 are designed to permit a constant rate of discharge of the respective condensers and so that the relays will be energised to move the respective switches to the left when discharge commences, but to be de-energised to allow the switches to revert to their right hand positions at predetermined potentials of the respective discharging condensers.

The waveform generator 1, the frequency of the output of which can be controlled by a suitable variable input parameter or signal 8, produces a voltage which cyclically increases and decreases uiformly with respect to time as indicated by the graph 1 of FIGURE 2. The amplitude of the waveform, and its mean value can be varied, and the minimum voltage of the waveform is greater than the predetermined potentials at which the condensers 3 and 6 will cause de-energising of the respective relays. The circuit of FIGURE 1, when supplied with this voltage waveform will cause continuous repeated alternate energisation and de-energisation of the relays of the two circuits 4 and 7, the switches 2 and 5 being repeatedly reversed in a sense opposite to each other. To initiate this operation however an initial movement must be caused of one of the switches in order to charge one of the condensers, since in the initial state, with both condensers discharged, both switches will be in their right hand positions, isolating the condensers from the supply 1. This can be effected either by a temporary mechanical movement of one of the swiches to its left hand position, over-riding its spring bias, for a time sufiicient for its condenser to become charged to a potential above its predetermined value, and then releasing it, or by temporarily energising one of the relays by an external current supply to effect such a movement of the respective switch.

Thus the circuit can be caused to operate, after switching on the generator 1, by moving switch 2 to its left hand position for a time sufficient for condenser 3 to receive a charge and reach a potential greater than its predetermined value for de-energising the relay of circuit 4, and then releasing the switch 2 so that it reverts to its right hand position under the influence of its spring. This movement is provided for by a press-button 9 arranged on depression to move the moving contact of switch 2 to its left hand position. 7 When switch 2 reverts to its right hand position on release of the press button 9 (the relay of circuit 7 still being de-energised) condenser 3 will discharge through circuit 4, energising the relay of that circuit so that switch is moved to its left hand position and condenser 6 is connected to the generator 1 and becomes charged. When condenser 3 has discharged to the predetermined potential, the relay of discharge circuit 4 will be de-energised, permitting switch 5 to revert to its right hand position. Condenser 6 then discharges through discharge circuit 7, energising the relay of that circuit, and moving switch 2 again to its left hand position. The relays have now executed a complete cycle of operation, and this cycle will be repeated continuously so long as the generator 1 is switched on.

The various potentials of the circuit components and the operation of the relays are illustrated graphically by FIGURE 2. Graph 1 shows the waveform output of the generator 1 (which, for this simple example, is assumed to be of constant frequency throughout). Graphs 2 and 3 show the potential-time variation of condensers 3 and 6 respectively, each plotted on the same time scale as graph 1. The line V; on graph 2 represents the preset operating voltage for the relay in discharge circuit 4 and the line V on graph 3 represents the preset operating voltage for the relay in discharge circuit 7. Graph 4 shows the time intervals for which the relays of circuits 4 and 7 are energised, and indicates the randomness of these intervals. Thus the relay of discharge circuit 4 is energised for the times represented by the lines ab and c-a', during which times condenser 3 is discharging at a uniform rate and the potential of condenser 6 is following the generator waveform. The relay of circuit 7 is energised during the times represented by the lines bc and de, whilst condenser 6 is discharging at a uniform rate and the potential of condenser 3 follows the generator waveform. The graphs have been simplified by the omission of any time delay between the potential of the charging capacitors and the generator potential, and do not include the short time occupied by the change-over of the switches.

The operation of either or both of the relays is utilised to provide the desired random signal output. For example the relays of discharge circuits 4 and 7 are provided with additional sets of contacts 11 and 12 operating simultaneously with the switches 5 and 2, and these contacts can be connected in another circuit to produce some intermittent operation of that circuit for performing a desired function, such as the operating of a slubbing mechanism in a textile yarn spinning apparatus, in sequence with the random energisation and de-energisation of the relay of circuit 4.

Since the circuits 4 and 7 provide for uniform rate of discharge of the respective condensers, it follows that the time At for which a relay is energised is proportional to the potential increase of the respective condenser above its predetermined value at the instant at which discharge of the condenser commences. Thus the maximum value of At, (At will follow when one or the other of the condensers have been charged to the maximum voltage of the waveform and the minimum possible value for At (Ar will follow when one or the other of the condensers has been charged to the minimum voltage of the waveform.

Using a triangular waveform of constant maximum and minimum voltages, and discharge circuits giving a uniform rate of discharge of condensers 3 and 6, there is an equal probability that any time interval, within the range Ai to At will occur. Thus a plot of the probability W of a given At occurring as ordinate, against At as abscissa would be as sketched in FIGURE 6. The amplitude of the waveform determines the values of At and At and the mean amplitude determines the mean value of At.

The above explanation based on a constant frequency for the waveform input illustrates the essential features of the invention, but it will be appreciated that under such operating conditions a particularly unfortunate choice of circuit components might result in the sequence of occurrences repeating after a comparatively small number of such occurrences. Preferably therefore the frequency of the waveform is changed at intervals by having a series of fixed frequencies (not related harmonically to each other) for the generator 1 and selecting them in turn. The overall shape of FIGURE 6 will be unaffected by the particular frequencies employed or the sequence in which they are selected.

The overall shape of FIGURE 6 will be affected, however by variations in the shape of the waveform generated (for example triangular or sinusoidal) and to reduce thepossibility that distortions of the waveform occurring when a change of frequency is made might affect the overall shape of FIGURE 6, the selections of frequencies are preferably made in synchronism with the switching of the relays for example by means of a frequency selector switch 13 operated to change the frequency control of the input parameter 8 by the relay of circuit 7.

If it is desired to avoid any tendency for an increasing or decreasing train of successive values of At to be generated, the maximum period of the waveform should be chosen to be less than Ar A circuit for generating several random signals to control a number of variables simultaneously may be built up from the basic circuit described.

A more comprehensive circuit designed to generate a signal train for controlling the thickness, length and spacing of slubs in textile threads will now be described with reference to FIGURES 3 and 4.

Referring to FIGURE 3, the circuit comprises three triangular waveform generators 20, 21 and 22. The waveform from generator 20 is fed through two-way switches 23 and 29 to condensers 26 and 27 respectively. The operation of switches 23 and 29 is controlled by the energisation and de-energisation of the relays in discharge circuits 25 and 24 respectively, in a manner identical with that described with reference to FIGURE 1. Condensers 36 and 31 are connected, by way of two-way switches 30 and 32 respectively, between generator 21 and relay-containing discharge circuit 28. Switches 30 and 32 are operated in accordance with the energisation and de-energisation of the relays in discharge circuits 24 and 25 respectively. Two-way switch 34 connects condenser 33 alternately to generator 22 and, by means of a two-way switch 35, to line 37. Switches 34 and 35 move in opposition to each other and are moved simultaneously by the relay in discharge circuit 28. A convenient reference potential 8,, is applied to line 41}. An output line 37 leads to the operating mechanism of a conventional slub-producing apparatus (not shown). The various inter-connections of the relays and switches have been shown with dotted lines.

This circuit produces a signal train such as that shown in FIGURE 4 which consists of a series of voltage pulses shown plotted graphically against time. The slub-producing apparatus connected to line 37 operates in a manner such that the thickness of the slub is controlled by the magnitude S of the pulse, the length of the slub is controlled by the length l of the pulse and the spacing between successive slubs is controlled by the spacing at between successive pulses.

The sequence of operations of the circuit shown in FIGURE 3 to produce the signal train illustrated in FIG- URE 4, in which S, l and a each vary in random fashion between preset limits, will now be described.

The circuit is shown in an ON state with the switches in their illustrated positions, and for the purpose of this description it will be assumed that condenser 26 has already started discharging through circuit 24. Thus the energisation of the relay in circuit 24 has already occurred and switches 29 and 30 have been moved to their left hand positions as illustrated. At the moment t (see FIGURE 4) condenser 26 reaches its predetermined potential or discharge level thereby de-energising the relay in circuit 24 causing it to operate to return switch-es 29 and 30 to their right hand positions. This connects newly charged condensers 27 and 36 to discharge circuits 25 and 28 respectively thereby energising the relays in these circuits. This energisation causes the relay in discharge circuit 25 to move switches 23 and 32 to their left hand positions, connecting condensers 26 and 31 to generators and 21 respectively for charging them. It also causes the relay in discharge circuit 28 to move switches 34 and 35 to connect condenser 33 to output line 37. Line 37 is therefore switched from the reference voltage S to the voltage S to which the condenser 33 had been charged by the generator 22 at the moment the switch 34 was thrown. This voltage S determines the thickness of the slub produced.

Condensers 36 and 27 continue to discharge through their respective discharge circuits. At the moment 2 the potential of condenser 36 has reached the predetermined value and the relay in circuit 28 becomes de-energised and operates to return switches 34 and 35 to their illustrated positions and the potential of line 37 returns to S The length l of the pulse has therefore been determined by the elapsed time between the operations of the relay in discharge cincuit 28 (see FIGURE 4),

Simultaneously with the discharge of condenser 36, condenser 27 continues to discharge through circuit 25 until at the moment 1 the potential of condenser 27 reaches its predetermined value. This de-energises the relay in circuit 25 which operates to return switches 23 and 32 to their illustrated positions. This connects charged condensers 26 and 31 to relay discharge circuits 24 and 28 respectively, energising the relays contained therein so as to move switches 34 and 35 to connect condenser 33 once more to line 37 causing a new voltage pulse to be applied to line 37, and to move switches 29 and 30 to their left hand positions.

At time i the charge on condenser 31 has reached its predetermined value thereby de-energising the relay in circuit 28 which operates to reconnect line 37 to potential S and condenser 33 to generator 22; as illustrated.

Condenser 26 continues discharging through circuit 24 until its potential reaches a predetermined value which occurs at time t This operates the relay in circuit 24 toreturn switches 29 and 30 to their right hand positions to begin a new cycle which produces voltage pulses in the line 37 at the times t and t and the cycle will thereafter be repeated with random variation of the duration, time and amplitude of the pulses so long as the generators 20, 21 and 22 remain switched on.

If the circuit of FIGURE 4 were in an OFF state switches 23, 29, 30 and 32 would all be in their right hand positions as mentioned hereinbefore in connection with FIGURE 1. T 0 start the circuit of FIGURE 4, switch 23 may be moved to the left and then to the right in the manner described for switch 2 of FIGURE 1.

Generator 22 may be omitted and the output potential for line 37 derived from generator 21. To avoid a permanent relation between the thickness and length of the clubs however, the potential to determine the magnitude S of the pulse should be picked Off at a different time from the potential determining the length of the slub. In practice it is convenient to pick ofi the potential S at the end of each output pulse, and this requires the use of a memory circuit such as that illustrated in FIGURE 5, which shows a modification of the lower and right hand parts of the circuit of FIGURE 4.

The relay-containing discharge circuit 28 is in circuit with generator 21' in the same manner as relay circuit 28 with generator 21 in FIGURE 3. The relay in circuit 28 controls two-way switches 34' and 35' which are shown in the positions they occupy when the relay is energised. In this condition generator 21 is connected to a condenser 31' to impose a charge thereon, and the output line 37 is connected to a condenser 38 which has previously been charged and discharges to the line 37' producing a pulse. At a time if condenser 36 has reached its predetermined potential and relay 28 is de-energised, reversing switches 34' and 35' so that line 37 is connected to line 44),

ending the pulse, and condenser 33' in connected to share its charge with a second condenser 38. At the next energising of the relay of circuit 28, at time t when condenser 31 is connected to discharge through the circuit, switches 34 and 35' are again reversed so that condenserr33' is re-charged and the charge acquired by condenser 38' is supplied to the output line 37, producing a further pulse. Thus the potential S of the further pulse is determined by the charge acquired by condenser 33 when it was being charged during the first pulse between times t and t To prevent a reduction in output potential due to the charge sharing between condensers 33' and 38, a buffer amplifier 39 is connected so as to be in series with the condensers during the charge sharing.

What I claim is:

1. In a control system, a first waveform generator, first charge storage means, first discharge storage means including a first relay, second charge storage means, second discharge means including a second relay, connecting means operated by said second relay for alternately connecting said first storage means to said generator and said first discharge means, and connecting means operated by said first relay for alternately connecting said second charge storage means to said generator and said second discharge means, a second waveform generator, a third and a' fourth charge storage means, third discharge means including a third relay, connecting means operated by said first relay for alternately connecting said third storage means to said second generator and said third discharge means, connecting means operated by said second relay for alternately connecting said fourth storage means to said second generator and said third discharge means, and output means controlled by said third relay.

2. The combination claimed in claim 1 wherein said output means comprises a third waveform generator, a fifth charge storage means, an output terminal and connecting means operated by said third relay for alternately connecting said fifth charge storage means to said third waveform generator and said output terminal.

References Cited by the Examiner UNITED STATES PATENTS 2,201,031 5/1940 Eichelberg 307132 2,271,418 1/1942 Eaglesfield 32815 X 2,580,673 1/1952 Graham 32815 X 2,870,332 1/1959 Mills 328-15 X MILTON O. HIRSHFIELD, Primary Examiner.

I. J. SWARTZ, Assistant Examiner. 

1. IN A CONTROL SYSTEM, A FIRST WAVEFORM GENERATOR, FIRST CHARGE STORAGE MEANS, FIRST DISCHARGE STORAGE MEANS INCLUDING A FIRST RELAY, SECOND CHARGE STORAGE MEANS, SECOND DISCHARGE MEANS INCLUDING A SECOND RELAY, CONNECTING MEANS OPERATED BY SAID SECOND RELAY FOR ALTERNATELY CONNECTING SAID FIRST STORAGE MEANS TO SAID GENERATOR AND SAID FIRST DISCHARGE MEANS, AND CONNECTING MEANS OPERATED BY SAID FIRST RELAY FOR ALTERNATELY CONNECTING SAID SECOND CHARGE STORAGE MEANS TO SAID GENERATOR AND SAID SECOND DISCHARGE MEANS, A SECOND WAVEFORM GENERATOR, A THIRD AND A FOURTH CHARGE STORAGE MEANS, THIRD DISCHARGE MEANS INCLUDING A THIRD RELAY, CONNECTING MEANS OPERATED BY SAID FIRST RELAY FOR ALTERNATELY CONNECTING SAID THIRD STORAGE MEANS TO SAID SECOND GENERATOR AND SAID THIRD DISCHARGE MEANS, CONNECTING MEANS OPERATED BY SAID SECOND RELAY FOR ALTERNATELY CONNECTING SAID FOURTH STORAGE MEANS TO SAID SECOND GENERATOR AND SAID THIRD DISCHARGE MEANS, AND OUTPUT MEANS CONTROLLED BY SAID THIRD RELAY. 